KC-46 TANKER 

AIRCRAFT

Program Generally on 

Track, but Upcoming 

Schedule Remains 

Challenging

Report to Congressional Committees

April 2014

GAO-14-190

United States Government Accountability Office
United States Government Accountability Office

Highlights of GAO-14-190, a report to 

congressional committees

April 2014

KC-46 TANKER AIRCRAFT

Program Generally on Track, but Upcoming Schedule 

Remains Challenging

Why GAO Did This Study

Aerial refueling allows U.S. military 

aircraft to fly farther, stay airborne 

longer, and transport more weapons, 

equipment, and supplies. Yet the 

mainstay of the U.S. tanker forces—

the KC-135 Stratotanker—is over 50 

years old. It is increasingly costly to 

support and its age-related problems 

could potentially ground the fleet. As a 

result, the Air Force initiated the $51 

billion KC-46 program to replace the 

aerial refueling fleet. The program 

plans to produce 18 tankers by 2017 

and 179 aircraft in total.

The National Defense Authorization 

Act for Fiscal Year 2012 mandated 

GAO to annually review the KC-46 

program through 2017. This report 

addresses (1) progress made in 2013 

toward cost, schedule, and 

performance goals, (2) development 

challenges, if any, and steps to 

address them, and (3) progress made 

in manufacturing the aircraft. To do 

this, GAO reviewed key program 

documents and discussed 

development and production plans and 

results with officials from the KC-46 

program office, other defense offices, 

and the prime contractor, Boeing.

What GAO Recommends

GAO recommends that the Air Force 

determine the likelihood and potential 

effect of delays on total development 

costs, and develop mitigation plans, as 

needed, related to potential delays. 

DOD concurred with the 

recommendation.

What GAO Found

The KC-46 program has made good progress over the past year—acquisition 

costs have remained relatively stable, the critical design review was successfully 

completed, the program is on track to meet performance parameters, and the 

contractor started building development aircraft. As shown, total program 

acquisition costs—which include development, production, and military 

construction costs—and unit costs have changed less than 1 percent since 

February 2011. 

Initial and Current KC-46 Program Quantities and Acquisition Costs

(then-year dollars in millions)

Initial estimate Current estimate Change

Total quantities 179 179 0

Total program acquisition costs $51,700.2 $51,376.8 <1%

Average program acquisition unit cost $288.8 $287.0 <1%

Source: GAO presentation of Air Force data.

As of December 2013, Boeing had about $75 million of its management reserves 

remaining to address identified, but unresolved development risks. There are 

indications that the start of initial operational test and evaluation, which is 

scheduled for May 2016, may slip 6 to 12 months. According to the Director of 

Operational Test and Evaluation, more time may be needed to train aircrew and 

maintenance personnel and verify maintenance procedures.

The program released over 90 percent of the KC-46 design drawings at the 

critical design review, indicating that the design is stable. Overall, development of 

about 15.8 million lines of software code is progressing mostly according to plan. 

The next 12 months will be challenging as the program must complete software 

development, verify that the software works as intended, finalize developmental 

flight test planning, and begin developmental flight tests. Software problem 

reports are increasing and Boeing could have difficulty completing all testing if 

more retests are needed than expected. Developmental flight testing activities 

are also a concern due to the need for extensive coordination among 

government agencies, the need for timely access to receiver aircraft (aircraft the 

KC-46 will refuel while in flight), and the aggressive test pace. The program office 

is conducting test exercises to mitigate risks and working with Navy and United 

Kingdom officials to finalize agreements to have access to necessary receiver 

aircraft.

The program has also made progress in ensuring that the KC-46 is ready for low 

rate initial production in 2015. Boeing has started manufacturing all four 

development aircraft on schedule. The program office has identified its critical 

manufacturing processes and verified that the processes are capable of 

producing key military subsystems in a production representative environment. In 

addition, the program has established a reliability growth curve and will begin 

tracking its progress towards reaching reliability goals once testing begins. 

Boeing is experiencing some manufacturing delays due to late supplier deliveries 

on the first aircraft and parts delays for a test article of a critical aerial refueling 

subsystem, but the program has not missed any major milestones. View GAO-14-190. For more information, 

contact Michael J. Sullivan at (202) 512-4841 

or sullivanm@gao.gov.
Page i GAO-14-190 KC-46 Tanker Aircraft

Letter 1 

Background 2

Program Is Continuing to Meet Cost, Schedule, and Performance 

Estimates 6

Program Stabilized the KC-46 Design and Is Now Focused on 

Software Development and Testing Challenges 11

Manufacturing Has Begun with Some Delays 16

Conclusions 23

Recommendation for Executive Action 23

Agency Comments 24

Appendix I Objectives, Scope, and Methodology 26

Appendix II Comparison of Current KC-135 Versus Planned KC-46 Performance 

Capabilities 28

Appendix III Description of Key Performance Parameters 29

Appendix IV KC-46 Critical Technology Elements 30

Appendix V Comments from the Department of Defense 31

Appendix VI GAO Contact and Acknowledgments 33

Tables

Table 1: Initial and Current KC-46 Program Quantities, Acquisition 

Costs, and Milestones 7

Table 2: Changes to the Planned Composition of KC-46 Software 13

Table 3: Activities to Capture Manufacturing Knowledge 20

Contents
Page ii GAO-14-190 KC-46 Tanker Aircraft

Figures

Figure 1: Conversion of Boeing 767 into a KC-46 Aerial Refueling 

Tanker 5

Figure 2: KC-46 Development Contract Management Reserve 

Allocation and Trend (as of December 2013) 10

Figure 3: KC-46 Engineering Design Drawing Completion Status 

through the Critical Design Review 12

Figure 4: Software Delivery Completed (as of January 2014) 14

Figure 5: KC-46 Tanker Production Time Line 18

Figure 6: Initial Reliability Growth Curve for 767-2C and KC-46 

Aircraft 21

Abbreviations

CDR critical design review 

DOD Department of Defense 

FAA Federal Aviation Administration

This is a work of the U.S. government and is not subject to copyright protection in the 

United States. The published product may be reproduced and distributed in its entirety 

without further permission from GAO. However, because this work may contain 

copyrighted images or other material, permission from the copyright holder may be 

necessary if you wish to reproduce this material separately.
Page 1 GAO-14-190 KC-46 Tanker Aircraft

441 G St. N.W.

Washington, DC 20548

April 10, 2014

Congressional Committees

The KC-46 tanker modernization program, valued at $51 billion, is the Air 

Force’s highest acquisition priority. The program recently completed its 

third year in development to convert an aircraft designed for commercial 

use into an aerial refueling tanker.1 Aerial refueling—the transfer of fuel 

from airborne tankers to combat and airlift forces—is critical to the U.S. 

military’s ability to project power overseas and to effectively operate 

within a combat theater. It enables military aircraft to fly farther, stay 

airborne longer, and transport more weapons, equipment, and supplies 

than unrefueled forces. KC-46 aircraft are expected to replace over forty 

percent of the KC-135 Stratotanker fleet, currently the mainstay of the 

U.S. tanker force. This force is now over 50 years old on average and 

costs increasingly more to maintain and support, with additional concerns 

that age-related problems could potentially ground the fleet. The Air Force 

plans to develop, test, and field 18 KC-46 tankers by August 2017, and 

eventually field a total of 179 aircraft.

The National Defense Authorization Act for Fiscal Year 2012 requires that 

we annually review and report on the KC-46 program through 2017.2 This 

is our third report reviewing the KC-46 development program. In our first 

report, we recommended that the Department of Defense (DOD) track 

lessons learned, since the KC-46 is one of the few major programs to 

award a fixed price incentive (firm target)3 development contract in recent 

years.4 We also recommended fully implementing sound metrics so 

planned key performance parameters could be measured appropriately. 

Subsequently, the program office took steps to do so. In our second 

 

1 The KC-46 designation refers to the acquisition program, while the actual tanker aircraft 

being procured is designated the KC-46A. For purposes of this report, we will use the KC46 designation throughout.

2 Pub. L. No. 112-81 § 244 (2011).

3 A fixed price incentive contract provides for adjusting profit and establishing the final 

contract price by a formula based on the relationship of final negotiated total cost to total 

target cost. FAR §§ 16.204 and 16.403-1.

4 GAO, KC-46 Tanker Aircraft: Acquisition Plans Have Good Features but Contain 

Schedule Risk, GAO-12-366 (Washington, D.C.: Mar. 26, 2012).
 

Page 2 GAO-14-190 KC-46 Tanker Aircraft

report, we recommended that DOD analyze the root causes for the rapid 

allocation of management reserves (funds set aside to address 

development risks) and improve the KC-46 master schedule to comply 

with best practices.5 DOD has since reviewed the use of management 

reserves and is conducting schedule risk assessments. In this third 

report, we (1) evaluate program progress toward cost, schedule, and 

performance goals; (2) identify program development challenges, if any, 

and steps to address these challenges; and (3) assess progress in 

manufacturing aircraft. The National Defense Authorization Act for Fiscal 

Year 2012 also requires that we analyze the results of developmental and 

operational testing and any plans for correcting identified deficiencies. We 

have not yet assessed testing results and plans to correct identified 

deficiencies because flight testing has not officially begun.

To conduct work for our current review, we analyzed financial 

management documents; program budgets; risk assessments; technical 

performance indicators; flight test and manufacturing plans; and software 

development plan and metrics. We also analyzed program plans and 

discussed results with the Air Force’s KC-46 program office, other 

defense offices, and the prime contractor, the Boeing Company (Boeing). 

We visited Boeing’s commercial production line and its facilities for 

system integration and military modifications.

We conducted this performance audit from May 2013 to April 2014 in 

accordance with generally accepted government auditing standards. 

Those standards require that we plan and perform the audit to obtain 

sufficient, appropriate evidence to provide a reasonable basis for our 

findings and conclusions based on our audit objectives. We believe that 

the evidence obtained provides a reasonable basis for our findings and 

conclusions based on our audit objectives. See appendix I for more 

information on our scope and methodology.

In February 2011, Boeing won the competition to develop the Air Force’s 

next generation aerial refueling tanker aircraft, the KC-46. This program is 

one of a few weapon system programs to use a fixed price incentive (firm 

 

5 GAO, KC-46 Tanker Aircraft: Program Generally Stable but Improvements in Managing 

Schedule Needed, GAO-13-258 (Washington, D.C.: Feb. 27, 2013).

Background
 

Page 3 GAO-14-190 KC-46 Tanker Aircraft

target) contract for development in recent years.6 Defense officials stated 

that a fixed price incentive (firm target) contract was appropriate for the 

program because KC-46 development is considered to be a relatively 

low-risk effort to integrate mostly mature military technologies onto an 

aircraft designed for commercial use. The KC-46 development contract is 

designed to hold Boeing accountable for cost associated with the 

development of four test aircraft and includes options to manufacture the 

remaining production lots.7 The contract limits the government’s financial 

liability and provides the contractor incentives to reduce costs in order to 

earn more profit. Barring any changes to KC-46 requirements by the Air 

Force, the contract specifies a target price of $4.4 billion and a ceiling 

price of $4.9 billion, at which point Boeing must assume responsibility for 

all additional costs.8 We previously reported that both the program office 

and Boeing have estimated that development costs would exceed the 

contract ceiling price. As of March 2014, Boeing and the program office 

estimated costs would be over the ceiling price by about $271 million and 

$787 million, respectively. The program office estimate is higher because 

it includes additional costs associated with performance as well as cost 

and schedule risk.

In all, 13 production lots are expected to be delivered. The contract 

includes firm fixed price contract options for the first production lot in 2015 

and the second production lot in 2016, and options with not-to-exceed 

firm fixed prices for production lots 3 through 13. The contract also 

 

6 In the past, the Department of Defense (DOD) has typically used cost-reimbursement 

contracts for development wherein the government pays all allowable costs incurred by 

the contractor to the extent prescribed in the contract. Recent legislation and defense 

policy now emphasize the use of fixed price development contracts, where warranted, to 

limit the government’s exposure to cost increases.

7 For purposes of this report, a production lot refers to a set number of aircraft that must 

be built and delivered in a given time frame. For example, the first production lot includes 

seven aircraft that are scheduled to be built and delivered to the Air Force between August 

2015 and January 2017.

8 The KC-46 development contract with Boeing specifies an incentive ratio for sharing any 

savings in the event of under runs when the actual contract cost is less than the target 

cost, or the sharing of additional costs when the actual contract cost is greater than this 

target cost. The government’s share of any cost savings or cost overrun is 60 percent 

while Boeing’s share is 40 percent. This cost sharing arrangement ends when the actual 

contract cost reaches a level that invokes the contract ceiling price of $4.9 billion, at which 

point the contractor is responsible for all additional costs.
 

Page 4 GAO-14-190 KC-46 Tanker Aircraft

requires Boeing to deliver 18 operational aircraft by August 2017.9 In 

addition, all required training must be complete, and the required support 

equipment and sustainment support in place by August 2017. Contract 

provisions also specify that Boeing must correct any required deficiencies 

and bring development and production aircraft to the final configuration at 

no additional cost to the government. After the first two production lots, 

the program plans to produce aircraft at a rate of 15 aircraft per year, with 

the final 6 aircraft procured in fiscal year 2027. Separate competitions 

may occur for later acquisitions, nominally called the KC-Y and KC-Z, to 

replace the rest of the KC-135 fleet and the KC-10 fleet (the Air Force’s 

large tanker).

Boeing plans to modify the 767 aircraft in two phases to produce a 

militarized aerial refueling tanker:

• In the first, Boeing is modifying the 767 with a cargo door and an 

advanced flight deck display borrowed from its new 787 and calling 

this modified version the 767-2C. The 767-2C will be built on Boeing’s 

existing production line.

• In the second, the 767-2C will proceed to the finishing center to 

become a KC-46. It will be militarized by adding air refueling 

capabilities, an air refueling operator’s station that includes panoramic 

three-dimensional displays, and threat detection and avoidance 

systems. 

The Federal Aviation Administration (FAA) has previously certified 

Boeing’s 767 commercial passenger airplane and will certify the design 

for both the 767-2C and the KC-46. Boeing established plans for the FAA 

to accomplish the 767-2C and the KC-46 certifications concurrently rather 

than consecutively, which is the typical procedure. The Air Force also has 

to certify the KC-46 and will use the FAA’s findings to make the overall 

airworthiness determination. See Figure 1 for a depiction of the 

conversion of the 767 aircraft into the KC-46 tanker.

 

9 According to program officials, Boeing plans to use the 4 development aircraft, the 7 

aircraft in the first production lot, and 7 of the aircraft in the second production lot in order 

to meet the contractual requirement to deliver 18 aircraft by August 2017.
 

Page 5 GAO-14-190 KC-46 Tanker Aircraft

Figure 1: Conversion of Boeing 767 into a KC-46 Aerial Refueling Tanker

The new KC-46 tanker is expected to be more capable than the KC-135 it 

replaces in several respects. Unlike the KC-135, it will allow for two types 

of refueling to be employed in the same mission—a refueling boom that is 

integrated with a computer assisted control system, as well as a 

permanent hose and drogue refueling system.10 The KC-135 has to land 

and switch equipment to transition from one mode to another. Also, the 

KC-46 is expected to be able to refuel in a variety of night-time and covert 

mission settings and will have countermeasures to protect it against 

infrared missile threats. The KC-135 is restricted in tactical missions and 

does not have sufficient defensive systems relative to the KC-46. 

Designed with more refueling capacity, improved efficiency, and 

increased cargo and medical evacuation capabilities than its predecessor, 

the KC-46 is intended to provide aerial refueling to Air Force, Navy, 

Marine Corps, and allied aircraft. Appendix II compares, in more detail, 

 

10 Currently, Air Force fixed-wing aircraft refuel with the “flying boom.” The boom is a rigid, 

telescoping tube that an operator on the tanker aircraft extends and inserts into a 

receptacle on the aircraft being refueled. Air Force helicopters and all Navy and Marine 

Corps aircraft refuel using the “hose and drogue.” The “hose and drogue” system involves 

a long, flexible refueling hose stabilized by a drogue (a small windsock) at the end of the 

hose. The pilot of the receiving aircraft maneuvers and connects to the hose. 
 

Page 6 GAO-14-190 KC-46 Tanker Aircraft

the current capabilities of the KC-135 with the planned capabilities of the 

new KC-46 tanker.

KC-46 total program acquisition costs (development, production, and 

military construction costs) have remained relatively stable since program 

start, changing less than 1 percent since February 2011, and the program 

is meeting schedule and performance goals. Boeing set aside $354 

million in contract funds to address identified, but unresolved 

development risks. As of December 2013, Boeing had about $75 million 

remaining to address these risks. Based on Boeing’s monthly usage, we 

calculate that the management reserves will be depleted about 3 months 

before the KC-46’s first flight and approximately 3 years before the 

development contract is completed. The government, however, would 

bear no financial risk for future work if Boeing uses all of its management 

reserves as long as the Air Force does not make changes to the KC-46 

requirements, schedule, or other relevant terms and conditions of the 

contract. Our prior work has found that flight testing is likely to uncover 

problems that will require management reserves to address.

The KC-46 total acquisition cost estimate has remained relatively stable 

since February 2011 although there have been some minor fluctuations 

among the development, procurement, and military construction costs 

that make up this estimate. The largest change is in the program’s 

development cost estimate, which has decreased by about $345 million, 

or about 5 percent. Development cost reductions can be attributed to 

fiscal year 2013 sequestration cuts, support for DOD’s Small Business 

Innovative Research fund, and cuts to a fund dedicated to tanker 

replacement.11 According to program officials, these reductions have not 

affected the program because it had set aside funds to address 

engineering changes, which have not occurred thus far. Overall, total 

acquisition and unit costs have decreased less than 1 percent and 

quantities have remained the same. Table 1 summarizes the initial and 

 

11 The absence of legislation to reduce the federal budget deficit by at least $1.2 trillion 

triggered the sequestration process in section 251A of the Balanced Budget and 

Emergency Deficit Control Act of 1985, as amended. Pursuant to the act, the President 

ordered sequestration of budgetary resources across non-exempt federal government 

accounts on March 1, 2013—5 months into fiscal year 2013.

Program Is 

Continuing to Meet 

Cost, Schedule, and 

Performance 

Estimates

Key Acquisition Cost, 

Schedule, and 

Performance Metrics Have 

Remained Relatively 

Stable
 

Page 7 GAO-14-190 KC-46 Tanker Aircraft

current estimated quantities, costs, and milestone dates for the KC-46 

program.

Table 1: Initial and Current KC-46 Program Quantities, Acquisition Costs, and Milestones

February 2011 October 2013 Change

Expected quantities

Development quantities 4 4 — 

Procurement quantities 175 175 — 

Total quantities 179 179 — 

Cost estimates (then-year dollars in millions)

Development $7,149.6 $6,804.5 -4.8%

Procurement $40,236.0 $40,321.4 0.2%

Military construction $4,314.6 $4,250.9 -1.5%

Total program acquisition $51,700.2 $51,376.8 -0.6%

Unit cost estimates (then-year dollars in millions)

Average program acquisition $288.8 $287.0 -0.6%

Average procurement $229.9 $230.4 0.2%

Key milestones

Program contract award (Milestone B) February 2011 February 2011 — 

Preliminary design review April 2012 April 2012 — 

Critical design review July 2013 July 2013 — 

Low rate initial production (Milestone C) August 2015 August 2015 — 

Initial operational test and evaluation start May 2016 May 2016 — 

Full rate production decision June 2017 June 2017 — 

Required assets available (18 aircraft operationally ready) August 2017 August 2017 — 

Source: GAO presentation of Air Force data.

The October 2013 development cost estimate of about $6.8 billion 

includes several contracts for various activities. For example, the program 

office awarded Boeing a contract for $4.9 billion to develop 4 test aircraft 

and budgeted over $0.3 billion for the development of aircrew and 

maintenance training systems.12 An estimated $1.6 billion is needed to 

cover other government costs, such as program office support, test and 

 

12 The Air Force awarded the Aircrew Training System contract in May 2013 to the 

FlightSafety Services Corporation for $78 million. The program office expects the 

maintenance training system contract to be awarded in fiscal year 2015.
 

Page 8 GAO-14-190 KC-46 Tanker Aircraft

evaluation support, contract performance risk, and other development 

risks associated with the aircraft and training systems. The procurement 

cost estimate of $40.3 billion is to procure 175 production aircraft, initial 

spares, and other support equipment. The military construction estimate 

of $4.2 billion includes the projected costs to build aircraft hangars, 

maintenance and supply shops, and other facilities to house and support 

the KC-46 fleet at 10 main operating bases, 1 training base, and the 

Oklahoma City Air Logistics Complex depot.

Boeing is also meeting the high level schedule milestones. Most recently, 

it conducted the critical design review (CDR) in July 2013, on schedule. 

However, there are indications that the start of initial operational test and 

evaluation, which is scheduled for May 2016, may slip. DOD’s Office of 

the Director, Operational Test and Evaluation, which is responsible for 

approving operational and live fire test and evaluation within each major 

defense acquisition program, recently issued its 2013 annual report and 

continued to recommend that the Air Force plan for a 6- to 12-month 

delay to the start of initial operational test and evaluation to allow more 

time to train aircrew and maintenance personnel and verify maintenance 

procedures. The KC-46 program office agrees that the test schedule is 

aggressive, but does not believe the delays are certain.

The program office projects that the KC-46 aircraft will meet the 

requirements of all nine key performance parameters by the end of 

development.13 Satisfying these key performance parameters will ensure 

that the KC-46 will be able to accomplish its primary mission of providing 

worldwide, day and night, adverse weather aerial refueling as well as its 

secondary missions. See appendix III for a list of the KC-46 key 

performance parameters. The program office has developed a set of 

metrics to help gauge its progress towards meeting the performance 

parameters. For example, one metric tracks operational empty weight 

because in general, every pound of excess weight equates to a 

corresponding reduction in the amount of fuel the aircraft can carry to 

accomplish its primary mission. Boeing currently projects that the aircraft 

will meet the weight target of 204,000 pounds.

 

13 Key performance parameters are performance attributes of a system considered critical 

to the development of an effective military capability. They are included verbatim in the 

acquisition program baseline and may be mandatory or selectively applied, depending on 

the system. 
 

Page 9 GAO-14-190 KC-46 Tanker Aircraft

At the outset of development, Boeing set aside $354 million from contract 

funds in a management reserve account, about 7 percent of the contract 

ceiling price, to address identified, yet unresolved, development risks. 

Last year we reported that Boeing had accomplished approximately 28 

percent of the development work and had allocated about 80 percent of 

the contract’s management reserves. We raised concerns about the high 

rate at which the management reserves were being used because doing 

so early in a program is often an indicator of future contract performance 

problems.

Since then, there have been two major actions related to management 

reserves in 2013. First, in January 2013, Boeing returned $72 million to 

the management reserves account because program officials determined 

that the program would pay for fuel for test flights rather than Boeing, new 

labor rates were lower than planned, and Boeing calculated costs 

associated with some types of labor incorrectly. Second, in August 2013, 

Boeing allocated about $42 million of its management reserves, with the 

largest portion, $24 million, used for a wet fuels laboratory. Boeing initially 

planned on using corporate funding for the wet fuels laboratory, which 

was intended for general wet fuels research. However, since the 

laboratory became more focused on meeting the specific needs of the 

KC-46 program, Boeing determined it was more appropriate to use 

management reserves. The other $18 million was used for a variety of 

other efforts, including minor design and architectural changes. The 

following figure illustrates management reserve allocation since program 

start and projects when reserves will be depleted.

Funding Set Aside to 

Alleviate Program Risk Is 

Almost Depleted
 

Page 10 GAO-14-190 KC-46 Tanker Aircraft

Figure 2: KC-46 Development Contract Management Reserve Allocation and Trend (as of December 2013)

As of December 2013, about $75 million in unallocated reserves remain. 

If the current usage trend continues—a monthly average of over $9 

million—the program office projects management reserves will be 

depleted in September 2014, about 3 months before the start of KC-46 

developmental flight testing and approximately three years before the 

development contract is completed. According to GAO’s Cost Estimating 

and Assessment Guide, significant use of management reserves early in 

a program may indicate contract performance problems and decreases 

the amount of reserves available for future risks, particularly during the 

test and evaluation phase when demand may be the greatest.14 Barring 

any changes to KC-46 requirements, schedule, or other relevant terms 

and conditions of the contract by the Air Force, Boeing would be solely 

 

14 GAO, GAO Cost Estimating and Assessment Guide: Best Practices for Developing and 

Managing Capital Program Costs, GAO-09-3SP (Washington, D.C.: March 2009).
 

Page 11 GAO-14-190 KC-46 Tanker Aircraft

responsible for the cost of future changes if it uses all of its management 

reserves, so the government bears no financial risk.

The program office and Boeing held the program’s CDR in July 2013 and 

released over 90 percent of the total engineering design drawings, a key 

indicator that the design is stable. The program is now focused on 

completing software development and integration, as well as test plans in 

preparation for developmental flight testing. Software development plans 

changed over the course of the past year in large part because the 

program solidified requirements at CDR and Boeing brought two of the 

program’s software intensive system components in-house and found 

ways to use some of its existing software. Overall, software development 

is progressing largely according to plan; however, software verification 

testing has not yet started and software problem reports are increasing. 

The flight test program is also a concern because it depends on 

coordination among several separate government entities, requires timely 

access to receiver aircraft (the aircraft the KC-46 will refuel while in flight), 

and requires a more aggressive pace than on past programs. The 

program office is conducting a series of rehearsal test exercises and is 

working with Air Force officials to finalize agreements related to receiver 

aircraft availability to mitigate these risks.

The program office held its CDR in July 2013, with Boeing releasing over 

90 percent of the total engineering design drawings. The 90 percent 

drawing release met a contractual requirement and is consistent with 

acquisition best practices that use this metric as an indicator that the 

design is stable. According to program officials, as of December 2013, 

Boeing had released 98.6 percent of the expected engineering design 

drawings and the remaining drawings relate almost exclusively to aircraft 

interiors and are not considered to be complex. Figure 3 shows the 

number of design drawings completed since Boeing began tracking it in 

May 2011.

Program Stabilized 

the KC-46 Design 

and Is Now Focused 

on Software 

Development and 

Testing Challenges

Program Successfully 

Completed Its Critical 

Design Review
 

Page 12 GAO-14-190 KC-46 Tanker Aircraft

Figure 3: KC-46 Engineering Design Drawing Completion Status through the Critical Design Review

Prior to CDR, the program office and Boeing took a number of steps to 

ensure the program had a stable design. This included holding a series of 

sub-system CDRs, replacing two system components that were not 

sufficiently mature, and addressing previously identified risks, such as 

aircraft weight. Currently, Boeing is working to alleviate lingering 

instability in key physical components related to aerial refueling—the 

centerline drogue system and wing aerial refueling pod. Boeing still 

considers the instability of these components to be a moderate program 

risk, and its strategy is to conduct modeling and simulation studies and 

perform ground tests to help mitigate this risk.
 

Page 13 GAO-14-190 KC-46 Tanker Aircraft

As of January 2014, Boeing estimates that 15.8 million lines of code will 

be needed for the KC-46. Boeing plans to rely primarily on reused 

software from its commercial aircraft for the 767-2C and more heavily on 

modified or new software for the military subsystems on the KC-46. As 

shown in table 2, the most recent plan is for Boeing to reuse existing 

software for 83 percent of its software needs, which has helped reduce 

risks associated with software development.

Table 2: Changes to the Planned Composition of KC-46 Software

Software type

Program

start 2011

Critical design

review 2013

Reused 76% 83%

Modified 18% 12%

New 6% 5%

Source: GAO presentation of KC-46 Air Force Program Office and Boeing data.

According to program officials, the changes in reused, modified, and new 

software between 2011 and 2013 are largely the result of the program 

solidifying requirements for CDR and Boeing’s effort to reduce the risk 

associated with the development of two software-intensive system 

components related to situational awareness. According to these officials, 

there were limitations with the original software developer’s software and 

Boeing ultimately decided to bring the development effort in-house, 

leveraging existing software code to mitigate risk.

Overall, we found that software development is currently progressing 

mostly according to Boeing’s plan. As shown in figure 4, as of January 

2014, Boeing reported that 73 percent of software had been delivered 

compared to its plan for having 76 percent at this time (96 percent of the 

planned activities).

Software Development Is 

Progressing
 

Page 14 GAO-14-190 KC-46 Tanker Aircraft

Figure 4: Software Delivery Completed (as of January 2014)

A large portion of the software that has been delivered to this point is 

reused software that is needed for the initial build of the 767-2C aircraft. A 

small amount of development work related to the aerial refueling 

software, about 3 percent, is behind schedule. The remaining software, 

related to key military subsystems for remote vision and situational 

awareness, among other capabilities, is expected to be delivered to 

Boeing through the beginning of June 2014.

While the program’s progress for software development is encouraging, 

program officials are expecting software verification testing, which has not 

yet begun, to be challenging. Notably, Boeing must verify the software 

code to determine if it works as intended. Approximately 735,000 lines of 

the code are new and relate in large part to key military unique systems. 

Moreover, Boeing’s software integration lab that simulates the KC-46 

cockpit will be at near capacity between February and June 2014. Boeing 

could have difficulty completing all testing if more retests are needed than 

expected.

Software Test Schedule 

Will Be Challenging
 

Page 15 GAO-14-190 KC-46 Tanker Aircraft

In addition to capacity concerns, we found that software problem reports 

are increasing. There were over 600 software problem reports as of 

January 2014 that needed to be addressed, which will add pressure to an 

integration lab already operating at near capacity. Thirty-five percent of 

the problem reports were considered urgent or high priority problems that 

need to be fixed as quickly as possible. Program officials stated that 

avionics flight management computer software has been a major 

contributor to the problem reports to date and that Boeing is working 

closely with this supplier to ensure problems are addressed. This 

particular supplier has recently increased the number of staff working on 

this software effort from 3 to 24 people to address the backlog of problem 

reports.

The program’s flight test schedule continues to be a concern due to the 

need for extensive coordination among government entities, the need for 

timely access to receiver aircraft, and its aggressive pace. The following 

is a summary of the various testing concerns and the steps, if any, the 

program office and Boeing are taking to address them.

• Coordinating on concurrent test activities: Government agencies and 

Boeing have agreed to a “test once” approach, whereby many of the 

test activities for FAA certification, developmental testing, aerial 

refueling, and operational testing will be combined to achieve greater 

efficiency.15 Currently, Boeing, the program office, the Air Force, 

Navy, FAA, and officials from the Office of the Secretary of Defense 

organizations for developmental and operational testing are finalizing 

detailed test plans, which are needed to guide flight test activities that 

are scheduled to begin in June 2014 for the 767-2C and in January 

2015 for the KC-46. The program office is conducting a series of 

rehearsal test exercises before any flight tests take place to ensure 

that all parties understand their roles and responsibilities during 

testing. Program officials report that three of four such exercises have 

been completed, with the next scheduled for September 2014. 

Officials said this exercise will focus on preparing for the KC-46’s first 

flight.

 

15 The program office reported that the expected number of tests as of February 2014 

includes, but is not limited to, 50 FAA certification-related test plans and 137 combined 

FAA and specification verification test plans. Additional non-FAA military certification and 

specification verification test plans are not yet available.

Pace of Flight Test 

Schedule Poses Future 

Risk
 

Page 16 GAO-14-190 KC-46 Tanker Aircraft

• Ensuring receiver aircraft availability: To meet the test schedule, 

receiver aircraft, such as the F-22 A and the F/A-18 C, are needed at 

certain locations and times to participate in the program’s test 

activities. The program office has finalized one memorandum of 

agreement with Air Force officials for access to 14 receiver aircraft 

and stated that it is currently in the process of developing two 

additional agreements with the Navy for two additional types of aircraft 

and the United Kingdom for their respective aircraft. If the receiver 

aircraft are not available when needed, the Air Force risks affecting 

Boeing’s test schedule.

• Maintaining flight test pace: The program office and Boeing report that 

maintaining the program’s flight test pace is among the program’s 

greatest risks. Program officials explained that this risk captures both 

the 65 hour per month commercial test pace for the 767-2C aircraft 

and the 50 hour per month military test pace for the KC-46 aircraft. To 

adhere to the aggressive test schedule, Boeing officials stated that 

they plan to fly development aircraft 5 to 6 days per week with roughly 

5 to 6 hours per mission (which DOD test organizations have shown is 

more aggressive for the military flight testing than other programs 

have demonstrated historically).16 Boeing officials believe they can 

achieve the test pace required because of Boeing’s testing experience 

with other commercial aircraft and the KC-10 tanker program. In 

addition, Boeing has local maintenance and engineering support

available to support the test program as well as control over flight test 

priorities for the commercial testing since the development aircraft are 

being tested at Boeing facilities.

The program has made progress in readying the KC-46 for low rate initial 

production in 2015. Boeing has started manufacturing all four 

development aircraft on schedule, but has experienced some delays with 

the first aircraft. The program office and Boeing have also taken several 

steps to capture the necessary manufacturing knowledge to make 

informed decisions as the program transitions from design into 

production. This includes identifying and assessing critical manufacturing 

processes to determine if they are capable of producing key military 

subsystems in a production representative environment. The program 

 

16 The first and third development aircraft have been assigned to participate in commercial 

flight tests and the second and fourth development aircraft will participate in the military 

flight tests. 

Manufacturing Has 

Begun with Some 

Delays
 

Page 17 GAO-14-190 KC-46 Tanker Aircraft

also established a reliability growth curve and Boeing will begin tracking 

its progress towards reaching reliability goals once testing begins. Boeing 

is making progress manufacturing most of the military unique 

subsystems, but a test article for a critical aerial refueling subsystem has 

been delayed by almost a year due to parts issues.

Boeing has started manufacturing all four development aircraft on 

schedule, but has experienced some delays with the first aircraft. The Air 

Force plans to eventually field a total of 179 aircraft no later than January 

2031. Figure 5 displays the time line for the manufacture of the 

development, low rate production, and full rate production aircraft.

Development Aircraft 

Manufacturing Has Started
 

Page 18 GAO-14-190 KC-46 Tanker Aircraft

Figure 5: KC-46 Tanker Production Time Line

Note: The low rate initial production end date in the figure above assumes that Milestone C will occur 

in August 2015. Based on that assumption, the contract requires that the last low rate production 

aircraft be delivered no later than March 2020. The full rate production end date assumes that the 

decision to proceed into full rate production will occur in June 2017. Based on that assumption, the 

contract stipulates that the last full rate production aircraft be delivered no later than January 2031.

Boeing began producing the first development aircraft (a 767-2C) in June 

2013, and Boeing officials said the aircraft was 76 percent complete as of 

mid January 2014. The aircraft was scheduled to be powered on for the 

first time in early December 2013, but program officials told us that 

activity has slipped until the end of April 2014. Boeing officials attributed 

the schedule slip to late supplier deliveries. Completion of major 

assembly operations has also slipped from mid January until mid March. 

Program officials told us that Boeing has been able to resequence tasks 
 

Page 19 GAO-14-190 KC-46 Tanker Aircraft

thus far to avoid affecting the critical path,17 such as adding the body fuel 

tanks to the first 767-2C earlier and in a different facility than originally 

planned. Program officials are assessing whether these delays will affect 

the timing of the first flight of the 767-2C, scheduled for June 2014.

Boeing and program officials said that manufacturing of the second 

development aircraft was going better than on the first aircraft, reporting 

that the aircraft was 65 percent complete as of mid January 2014. 

Officials added that there had been a 75 percent reduction in overall parts 

shortages. The third and fourth aircraft just began production in late 

October 2013 and mid January 2014, respectively. From the first to the 

fourth development aircraft, Boeing is anticipating improvement in its 

ability to manufacture the aircraft. For example, the first aircraft is 

scheduled to take about 11 and a half months from the start of major 

assembly until first flight while the fourth aircraft is only scheduled to take 

about 7 months. Once complete, the four development aircraft will then 

enter the finishing center at various points between June 2014 and 

September 2015 to be converted to a KC-46 tanker.

The program office and Boeing have taken several initial steps to help 

ensure that the KC-46 will be ready for low rate production in August 

2015 and that the aircraft will be reliable. In our prior work, we identified 

the activities required to capture manufacturing knowledge.18 These 

activities include (1) identifying key system characteristics and critical 

manufacturing processes; (2) establishing a reliability growth plan and 

goals; (3) conducting failure modes and effects analysis; (4) conducting 

reliability growth testing; and (5) determining whether processes are in 

control and capable. Table 3 provides a description of these activities and 

progress the program has made for each.

 

17 The critical path defines the program’s earliest completion date or minimum duration it 

will take to complete all activities.

18 GAO, Best Practices: Capturing Design and Manufacturing Knowledge Early Improves 

Acquisition Outcomes, GAO-02-701 (Washington, D.C.: July 15, 2002).

Program Is Capturing 

Manufacturing Knowledge
 

Page 20 GAO-14-190 KC-46 Tanker Aircraft

Table 3: Activities to Capture Manufacturing Knowledge

Activity description Program progress

Identify key system characteristics and critical manufacturing processes: A product’s key characteristics and 

critical manufacturing processes should be identified early. Because there can be thousands of 

manufacturing processes required to build a product, companies focus on the critical processes—those that 

build parts that influence the product’s key characteristics such as performance, service life, or 

manufacturability.

Completed

Set reliability growth plan and goals: A product’s reliability is its ability to perform over an expected period of 

time without failure, degradation, or need of repair. A growth plan is developed to mature the product’s 

reliability over time through reliability growth testing so that it has been demonstrated by the time production 

begins.

Completed

Conduct failure modes and effects analysis: Bottom-up analysis is done to identify potential failures for 

product reliability. It begins at the lowest level of the product design and continues to each higher tier of the 

product until the entire product has been analyzed. It allows early design changes to correct potential 

problems before fabricating hardware.

Initiated

Conduct reliability growth testing: Reliability growth is the result of an iterative design, build, test, analyze, 

and fix process for a product’s design with the aim of improving the product’s reliability over time. Design 

flaws are uncovered and the design of the product is matured.

Not Started

Determine processes in control and capable: Statistical process control is used to determine if processes are 

consistently producing parts. Once control is established, an assessment is made to measure the process’s 

ability to build a part within specification limits as well as how close the part is to that specification. A process 

is considered capable when it has a defect rate of less than 1 out of every 15,152 parts produced.

Not Started

Source: GAO. 

Since the 767-2C will be manufactured on Boeing’s existing 767 

production line, the program office and Boeing have focused their 

attention on identifying the key system characteristics and critical 

manufacturing processes for the military unique subsystems. Prior to 

CDR, the program office and Boeing completed assessments of 12 

critical manufacturing processes, such as the assembly of aerial refueling 

components. These assessments indicated that key military subsystems 

could be manufactured in a production representative environment. The 

program office and Boeing plan on conducting another assessment prior 

to August 2015 to determine if the program is ready to begin low rate 

initial production.

The program office has established a reliability growth curve and goal. To 

assess reliability growth, the program is tracking the mean time between 

unscheduled maintenance events due to equipment failure, which is 

defined as the total flight hours divided by the total number of incidents 

requiring unscheduled maintenance.19 These failures are caused by a 

 

19 Mean time between unscheduled maintenance is not a contractual metric.
 

Page 21 GAO-14-190 KC-46 Tanker Aircraft

manufacturing or design defect and require the use of Air Force 

resources, such as spare parts or manpower, in order to fix them. The 

program has set a reliability goal of 2.83 flight hours between 

unscheduled maintenance events, but does not expect that goal to be 

achieved until the program has logged 50,000 flight hours. Figure 6 below 

depicts how the program office expects the aircraft’s reliability to improve 

over the program’s initial 5,000 flight hours.

Figure 6: Initial Reliability Growth Curve for 767-2C and KC-46 Aircraft

The program expects to be above the idealized reliability growth curve at 

the start of testing because initial testing will be on a 767-2C, a derivative 

of a commercial aircraft that has been flying since the 1980s. Reliability is 

projected to fall below expectations once the military sub-systems are 

added to the aircraft. The program then expects the reliability to steadily 

improve to the point where the aircraft could fly about 2 hours between 

unscheduled maintenance events at the start of initial operational test and 

evaluation. As shown in figure 6 above, the program will be on the 

idealized reliability growth curve at that point.
 

Page 22 GAO-14-190 KC-46 Tanker Aircraft

Boeing has also initiated a failure modes and effects analysis that covers 

41 subsystems. Boeing and the program office rely on this analysis to 

determine which subsystems on the aircraft are likely to fail, when and 

why they fail, and whether those subsystems’ failures might threaten the 

aircraft’s safety. Boeing is also using this information to develop a tool to 

detect and log equipment failures. The program office plans to share the 

analysis with aircraft maintenance staff.

The program has not yet begun two critical manufacturing and reliability 

assessment activities. First, the program is not currently tracking reliability 

growth because the 767-2C first flight is not scheduled to take place until 

June 2014 and no flight hours have been accrued yet. Second, the 

program has not determined whether manufacturing processes are in 

control and capable of producing parts consistently with few defects. The 

program plans to review and verify that process controls are in place to 

ensure the quality of the manufacturing process as part of its next 

assessment of critical manufacturing processes prior to the low rate 

production decision in August 2015. Program officials said their review 

would be focused on whether these process controls are in place rather 

than analyzing the data to determine if the processes are actually in 

control.

Boeing is making progress manufacturing most of the military unique 

subsystems, such as the aerial refueling operator station, but the test 

refueling boom’s schedule has slipped by almost a year due to parts 

delays. Boeing’s original design included parts that proved challenging to 

fit within the boom’s space constraints, and other parts were redesigned 

to improve the boom’s safety. Boom parts suppliers, however, have 

experienced delays in delivering the redesigned parts to Boeing, which 

has prompted Boeing to send staff to help one of the suppliers minimize 

further schedule slips. Boeing officials told us they decided to build a test 

boom as a risk reduction effort and plan to apply lessons learned from 

producing the test boom to future boom production. However, program 

officials currently estimate that boom parts delays have also led to an 

approximately 1-month schedule slip in the first development aircraft’s 

boom. Boeing is facing some schedule pressure on this boom because it 

is now scheduled to be completed only a few days before the start of 

ground vibration testing. Boeing officials said they needed the boom for 

this testing and would like to complete ground vibration testing before the 

767-2C’s first flight. The second development aircraft’s boom is 

scheduled to be built in only 5 months. Based on its current schedule, 

Status of Key Military 

Subsystems
 

Page 23 GAO-14-190 KC-46 Tanker Aircraft

Boeing needs to have this boom completed by June 2014 in order to 

meet the KC-46’s first flight, scheduled for January 2015.

The KC-46 program has made good progress to date—acquisition costs 

have remained relatively stable, high-level schedule and performance 

goals have been met, the critical design review was successfully 

completed, and the contractor is building development aircraft. The next 

12 months will be challenging as the program must accomplish a 

significant amount of work and the margin for error is small. For example, 

the program is scheduled to complete software integration and the first 

test flights of the 767-2C and KC-46. The remaining software 

development and integration work is mostly focused on military software 

and systems and is expected to be more difficult relative to the prior work 

completed. The program’s test activities continue to be a concern due to 

its aggressive test schedule. Detailed test plans must be completed and 

the program must maintain an unusually high test pace to meet this 

schedule. Perhaps more importantly, agencies will have to coordinate to 

concurrently complete multiple air worthiness certifications. While 

efficient, this approach presents significant risk to the program. The 

program office must also finalize agreements now in progress to ensure 

that receiver aircraft are available when and where they are needed to 

support flight tests. Any discoveries made in testing that require design 

changes may negatively affect program schedule and delivery to the 

warfighter. Parts delays on the first development aircraft and a critical 

aerial refueling subsystem are also causing increased schedule pressure.

With these risks in its near future, the KC-46 program will continue to bear 

watching. While all of the risks currently appear to be recognized, any 

slips in software testing, flight testing, and manufacturing as the program 

moves forward could cause delays in the program.

Due to existing schedule risks and the fact that the program is entering a 

challenging phase of testing, we recommend that the Secretary of 

Defense direct the Air Force to study the likelihood and potential effect of 

delays on total development costs, and develop mitigation plans, as 

needed, related to potential delays.

Conclusions

Recommendation for 

Executive Action
 

Page 24 GAO-14-190 KC-46 Tanker Aircraft

DOD provided us with written comments on a draft of this report, which 

are reprinted in appendix V. DOD concurred with our recommendation. 

The KC-46 program office conducts an annual analysis of cost and 

schedule risks to quantify the potential effect of delays on program costs

and officials told us they will consider the risks we identified in that 

analysis. We also incorporated technical comments from DOD as 

appropriate.

We are sending copies of this report to the Secretary of Defense; the 

Secretary of the Air Force; and the Director of the Office of Management 

and Budget. The report is also available at no charge on the GAO website 

at http://www.gao.gov.

If you or your staff has any questions concerning this report, please 

contact me at (202) 512-4841 or sullivanm@gao.gov. Contact points for 

our Offices of Congressional Relations and Public Affairs may be found 

on the last page of this report. GAO staff contributing to this report are 

listed in appendix VI.

Michael J. Sullivan

Director

Acquisition and Sourcing Management

Agency Comments
 

Page 25 GAO-14-190 KC-46 Tanker Aircraft

List of Committees

The Honorable Carl Levin

Chairman

The Honorable James Inhofe

Ranking Member

Committee on Armed Services

United States Senate

The Honorable Richard Durbin

Chairman

The Honorable Thad Cochran

Ranking Member

Subcommittee on Defense

Committee on Appropriations

United States Senate

The Honorable Howard P. McKeon

Chairman

The Honorable Adam Smith

Ranking Member

Committee on Armed Services

House of Representatives

The Honorable Rodney Frelinghuysen

Chairman

The Honorable Peter Visclosky

Ranking Member

Subcommittee on Defense

Committee on Appropriations

House of Representatives
Appendix I: Objectives, Scope, and 

Methodology

Page 26 GAO-14-190 KC-46 Tanker Aircraft

This report examines the Air Force’s continued development of the KC-46 

tanker program. Specifically, we examined (1) progress toward cost, 

schedule, and performance goals; (2) development challenges, if any, 

and steps to address them; and (3) progress in manufacturing the aircraft.

To assess progress toward cost, schedule and performance goals in the 

calendar year of this review (2013), we reviewed briefings by program 

and contractor officials, financial management documents, program 

budgets, defense acquisition executive summary reports, selected 

acquisition reports, monthly activity reports, technical performance 

indicators, risk assessments, and other documentation. To evaluate cost 

information, we analyzed earned value management data and the 

contractor’s use of management reserves. To assess development 

schedule progress, we compared program milestones established at 

program start to current estimates and reviewed Defense Contract 

Management Agency monthly assessments of KC-46 schedule health 

and program office schedule analyses. We also interviewed program 

officials to determine the status of Department of Defense (DOD) efforts 

to implement our prior recommendations aimed at improving the 

program’s integrated master schedule. To measure progress toward 

performance goals, we reviewed current estimates of key performance 

parameters, key system attributes, and technical performance metrics 

and compared them to threshold and objective requirements. We 

discussed results of the initial KC-46 operational assessment with officials 

from the Air Force Operational Test and Evaluation Center and the 

Director of Operational Test and Evaluation. We also interviewed relevant 

officials from the KC-46 program office, Boeing, and the Department of 

Defense.

To assess development challenges and steps to address them, we 

examined program documentation, such as critical design review 

briefings, risk assessments and briefings, software metrics reports, 

integrated test team meeting minutes, and updates to key documents 

such as the technology maturation, software development, and integrated 

test plans. We also analyzed pertinent DOD documents including the 

Defense Contract Management Agency’s monthly program assessment 

reports, the first operational assessment by the Air Force Operational 

Test and Evaluation Center, and annual reports issued by the Deputy 

Assistant Secretary of Defense for Developmental Test and Evaluation 

and the Director of Operational Test and Evaluation. When possible, we 

attended integrated test team and program management meetings to 

obtain additional insight on any challenges or mitigation efforts being 

discussed by Boeing and program officials. In addition, we examined the 

Appendix I: Objectives, Scope, and 

Methodology
Appendix I: Objectives, Scope, and 

Methodology

Page 27 GAO-14-190 KC-46 Tanker Aircraft

program’s progress in completing design drawings and maturing critical 

technologies at the critical design review. Furthermore, we interviewed 

officials from Boeing, the program office, the Office of the Secretary of 

Defense, and the Department of the Navy to assess development 

challenges and the suitability of steps taken to address them.

To assess progress in manufacturing aircraft, we analyzed program office 

and Boeing documents, such as the manufacturing program plan; 

quarterly manufacturing and quality briefings; and program schedules. 

We used these documents to compare Boeing’s initial schedule for 

completing aircraft and boom manufacturing to its actual performance and 

to identify challenges, if any. We also evaluated whether the program 

captured manufacturing knowledge recommended in prior GAO best 

practices work. This included reviewing manufacturing readiness 

assessments and comparing the results and future plans to DOD 

guidance and manufacturing best practices identified in prior GAO work. 

Lastly, we interviewed Boeing and program officials to discuss 

manufacturing progress and challenges and conducted a site visit of 

Boeing’s 767 production line and its temporary and permanent boom 

production facility and finishing center.

We conducted this performance audit from May 2013 to April 2014 in 

accordance with generally accepted government auditing standards. 

Those standards require that we plan and perform the audit to obtain 

sufficient, appropriate evidence to provide a reasonable basis for our 

findings and conclusions based on our audit objectives. We believe that 

the evidence obtained provides a reasonable basis for our findings and 

conclusions based on our audit objectives.
Appendix II: Comparison of Current KC-135 

Versus Planned KC-46 Performance 

Capabilities

Page 28 GAO-14-190 KC-46 Tanker Aircraft

Appendix II: Comparison of Current KC-135 

Versus Planned KC-46 Performance 

Capabilities
Appendix III: Description of Key Performance 

Parameters

Page 29 GAO-14-190 KC-46 Tanker Aircraft

Key performance parameter Description 

Tanker Air Refueling Capability Aircraft shall be capable of accomplishing air refueling of all Department of Defense current 

and programmed (budgeted) receiver aircraft. The aircraft shall be capable of conducting 

both boom and drogue air refueling on the same mission. 

Fuel Offload versus Radius Aircraft shall be capable of carrying certain amounts of fuel (to use in air refueling) certain 

distances. 

Operate in Civil and Military Airspace Aircraft shall be capable of worldwide flight operations in all civil and military airspace. 

Airlift Capability Aircraft shall be capable of transporting certain amounts of both equipment and personnel. 

Receiver Air Refueling Capability Aircraft shall be capable of receiving air refueling from any compatible tanker aircraft. 

Force Protection Aircraft shall be able to operate in chemical and biological environments. 

Net-Ready Aircraft must be able to have effective information exchanges with many other Department of 

Defense systems to fully support execution of all necessary missions and activities. 

Survivability Aircraft shall be capable of operating in hostile threat environments. 

Simultaneous Multi-Point Refueling Aircraft shall be capable of conducting drogue refueling on multiple aircraft on the same 

mission. 

Source: GAO presentation of Air Force data.

Appendix III: Description of Key Performance 

Parameters
Appendix IV: KC-46 Critical Technology 

Elements

Page 30 GAO-14-190 KC-46 Tanker Aircraft

Critical technology Description Testing to date 

3-Dimensional Display The display screens at boom operator stations inside the aircraft 

provide the visual cues needed for the operator to monitor the 

aircraft being refueled before and after contact with the refueling 

boom or drogue. The images of the aircraft on the screens are 

captured by a pair of cameras outside the aircraft that are meant 

to replicate the binocular aspect of human vision by supplying an 

image from two separate points of view, replicating how humans 

see two points of view, one for each eye. The resulting image 

separation provides the boom operator with greater fidelity and a 

more realistic impression of depth, or a 3rd dimension. 

Similar technology has been used 

on two foreign-operated refueling 

aircraft and a representative model 

in tests with other Boeing tankers. 

Tactical Situational 

Awareness System 

Reactive Threat 

Avoidance—Route 

Generation Engine

The route generation engine is a component of the reactive threat 

avoidance sub-system. This sub-system monitors for ground and 

surface threats based on the aircraft’s location and the active 

flight route. It identifies threats that impact the current route, 

provides a safer alternative route, and alerts the pilot that a new 

route is available for review and acceptance.

A recent version of the route 

generation engine was flown and 

demonstrated on a Navy aircraft, but 

improvements have been made that 

have not been flight tested.

Source: GAO presentation of Air Force information.

Appendix IV: KC-46 Critical Technology 

Elements
Appendix V: Comments from the Department 

of Defense

Page 31 GAO-14-190 KC-46 Tanker Aircraft

Appendix V: Comments from the Department 

of Defense
Appendix V: Comments from the Department 

of Defense

Page 32 GAO-14-190 KC-46 Tanker Aircraft
Appendix VI: GAO Contact and 

Acknowledgments

Page 33 GAO-14-190 KC-46 Tanker Aircraft

Michael Sullivan (202) 512-4841 or sullivanm@gao.gov

In addition to the contact name above, the following staff members made 

key contributions to this report: Cheryl Andrew, Assistant Director; Jeff 

Hartnett; Katheryn Hubbell; John Krump; LeAnna Parkey; and Robert 

Swierczek.

Appendix VI: GAO Contact and 

Acknowledgments

GAO Contact

Acknowledgments

(121147)
The Government Accountability Office, the audit, evaluation, and 

investigative arm of Congress, exists to support Congress in meeting its 

constitutional responsibilities and to help improve the performance and 

accountability of the federal government for the American people. GAO 

examines the use of public funds; evaluates federal programs and 

policies; and provides analyses, recommendations, and other assistance 

to help Congress make informed oversight, policy, and funding decisions. 

GAO’s commitment to good government is reflected in its core values of 

accountability, integrity, and reliability.

The fastest and easiest way to obtain copies of GAO documents at no 

cost is through GAO’s website (http://www.gao.gov). Each weekday 

afternoon, GAO posts on its website newly released reports, testimony, 

and correspondence. To have GAO e-mail you a list of newly posted 

products, go to http://www.gao.gov and select “E-mail Updates.”

The price of each GAO publication reflects GAO’s actual cost of 

production and distribution and depends on the number of pages in the 

publication and whether the publication is printed in color or black and 

white. Pricing and ordering information is posted on GAO’s website, 

http://www.gao.gov/ordering.htm. 

Place orders by calling (202) 512-6000, toll free (866) 801-7077, or 

TDD (202) 512-2537. 

Orders may be paid for using American Express, Discover Card, 

MasterCard, Visa, check, or money order. Call for additional information.

Connect with GAO on Facebook, Flickr, Twitter, and YouTube. 

Subscribe to our RSS Feeds or E-mail Updates. Listen to our Podcasts. 

Visit GAO on the web at www.gao.gov. 

Contact:

Website: http://www.gao.gov/fraudnet/fraudnet.htm

E-mail: fraudnet@gao.gov

Automated answering system: (800) 424-5454 or (202) 512-7470

Katherine Siggerud, Managing Director, siggerudk@gao.gov, (202) 512-

4400, U.S. Government Accountability Office, 441 G Street NW, Room 

7125, Washington, DC 20548

Chuck Young, Managing Director, youngc1@gao.gov, (202) 512-4800

U.S. Government Accountability Office, 441 G Street NW, Room 7149 

Washington, DC 20548

GAO’s Mission

Obtaining Copies of 

GAO Reports and 

Testimony

Order by Phone

Connect with GAO

To Report Fraud, 

Waste, and Abuse in 

Federal Programs

Congressional 

Relations

Public Affairs

Please Print on Recycled Paper.